Imagine for a moment that it’s 2001, and you’re Jennifer Miller. You’re pregnant with your second baby, and an ultrasound shows that his heart isn’t developing normally: In fact, the left side of his heart has a problem so significant it will stop developing normally from that point on. Your unborn baby has a severe blockage of the aortic valve, known as stenosis, which will lead to a rare and potentially fatal condition called hypoplastic left heart syndrome (HLHS) at birth.

Now imagine that you’re Jack Miller. As you float in the quiet darkness of the womb, your heart is the size of a grape and that troublesome valve that won’t deliver blood from the left ventricle of your body is only as big as the head of a ballpoint pen.

What happened next put the Millers on the front page of the New York Times and in TIME magazine.